SYST:REM will turn on the REMOTE light. SYST:REMLock disables the front panel. SYST:REM is necessary first. Making a light change is a good first step.
Rs232 used levels from -25 to -3 and +3 to +25 for and has been relaxed. RS232 doesn't work well at +-5V. +-12 Is more normal for Rs232.
Who ever told you that +5 is a high? In the Rs323 World, negative voltages are high:
http://www.interfacebus.com/Design_Connector_RS232.html at the external interface.
A quick way to look at the specs are DSR/DTR say the interfaces have power.
CTS/RTS say that the interfaces say that they can accept/reject data (Hardware flow)
TD/RD where data is sent/received
RI - Ring indicator,the phone/modem is ringing
SG - Common
PG- Protective ground (usually not needed)
The standard got so mangled that anything is possible. Always use voltages at the connector.
A framing error is a MAJOR communication problem. Baud or flow, typically. It can also be the number of stop/start/data bits and/or parity.